This is hard to legally define.
When someone represents themselves as a lawyer, they must have a practicing certificate from their states Law Society, indicating they have been through a background check and have sufficient training.
When someone represents themselves as a Medical Practitioner (Doctor), they must be registered with AHPRA, indicating they have been through a full exemption police history check, background check, are qualified as a medical doctor and have kept their knowledge of medicine up to date with CPD.
If I called myself a Medical Practitioner or a Lawyer without being registered, I would be facing criminal charges that include fines and imprisonment as a penalty. But in the drug testing arena, we have no regulatory body and no minimum accreditation standard.
So how can you be sure the person performing testing services is to be trusted? Ask them for some things such as;
A copy of their relevant qualification (there are a few, but the younger testing officers will likely have HLTPAT005) - ensure it is from a Registered Training Organisation.
An ACIC Criminal History Check. Whilst these checks are very cursory and will not reveal their whole history, only recorded convictions, it can be reassuring to know they are not fresh out of prison.
The details of their supplier, the drug/alcohol testing equipment suppliers will be able to verify how long they have been in business for and how reliable they are.
Calibration certificates - any electronic testing equipment.
What happens if you engage an unqualified/untrained testing officer;
If they advised a person was positive or negative for a drug, any such remark must be disregarded as they would not be able to prove before a court they have the skills, knowledge and expertise to determine a person is either positive or negative.
If you dismissed staff on the advice of an unqualified individual, I imagine the Fair Work Commission would not show much mercy and would order restitution in the tens of thousands for lost wages and emotional damages etc. Keep in mind, whether or not the employee was on drugs would become immaterial as a good solicitor would solely rely on your failure to ensure the testing was fair, reasonable, safe and competently administered.
The tests likely won't comply with any relevant Australian Standards which for companies that require that (i.e. transport, mining, healthcare) means your relevant regulatory body may discipline you for engaging an unqualified service.
A drug testing officer can be anyone. Going with large companies can be a good way to avoid disreputable persons testing your staff, however due to the excessive fees these individuals charge, small businesses are more likely to engage an individual and sadly, will just pick whoever is cheaper.
As it was learned in the matter of Greene v Lincoln Logistics Pty Ltd, an improperly conducted drug test costs a company thousands per employee tested, even if that employee was on drugs and had cheated on the test.
I would define a drug testing officer as someone who is sufficiently experienced, qualified and compliant with Australian Standards.
If you would like to see changes, speak to your local member of parliament about regulation of Drug Testing officers under Work Health and Safety legislation. Whilst NSW can be a nanny state with everything from banning toys (legal elsewhere in Australia) to Walking on the wrong side of the road, but I genuinely feel this sector is unregulated and it would be great to just have an offence made, like they did with paramedics in 2015, that unless you are qualified you cannot call yourself a drug testing officer.